Different types of MEMS electrostatic micro-actuators have been used to achieve Autofocus (AF) and Optical Image Stabilization (OIS) in miniature cameras. U.S. Pat. No. 9,264,591B2 discloses a MEMS electrostatic actuator to achieve OIS and AF by providing a multiple degrees of freedom (DOF) motion to move the image sensor. The actuator also utilizes mechanical flexures/springs between the driving comb electrodes and the load stage for the purpose of amplifying the rotational strokes and to reduce the coupling effect between motion along different axes. Such a structure, having elastic flexures between the load and driving electrodes, significantly reduces the electrostatic forces acting on the load. It also introduces a mechanical coupling between different motions as one set of springs (i.e. four mechanical springs) are responsible to move a single load along multiple axes.
Another MEMS electrostatic actuator that is used to achieve OIS in miniature cameras is presented in U.S. Pat. No. 9,578,217B2. The actuator is able to move the image sensor along 3-DOF in-plane motion, i.e., translation along the x and y axes and rotation about the z-axis to achieve OIS. The actuator is not able to provide yaw motion (rotation about the x-axis) and pitch motion (rotation about the y-axis) to the image sensor. It has been reported that providing yaw and pitch motion to the optical image sensor or the entire module is the best way to counteract the hand-shaking rotation components (yaw and pitch).